Defects in half-Heusler type antimonides ScTSb (T = Ni, Pd, Pt)

The ScTSb (T = Ni, Pd, Pt) antimonides adopt the cubic MgAgAs type structure (F¯43mF¯43m, a = 605.21(6), wR2 = 0.0241, 94 F2 values and 7 variables for ScNi0.871(6)Sb; a = 630.00(6), wR2 = 0.0254, 147 F2 values and 7 variables for ScPd0.966(3)Sb; a = 631.1(1), wR2 = 0.0220, 89 F2 values and 5 variables for ScPtSb). The refinement of the occupancy parameters revealed vacancies on the transition metal sites for the Ni and Pd compounds. This results in additional signals in the 45Sc MAS NMR spectra, having intensities in accordance with the refined vacancy concentrations. Furthermore, the quenched samples are showing a third 45Sc resonance that vanishes upon annealing, suggesting a partly disordered transition metal substructure. The higher degree of ordering due to annealing is also manifested by a reduction of the central transition line widths in the 121Sb MAS NMR spectra. 121Sb Mössbauer spectra are showing a single absorption line for all samples.

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